| Message ID | 1460373568-4374-1-git-send-email-ard.biesheuvel@linaro.org |
|---|---|
| State | New |
| Headers | show |
On Mon, Apr 11, 2016 at 01:19:28PM +0200, Ard Biesheuvel wrote: > If both ACPI and DT platform descriptions are available, and the > kernel was configured at build time to support both flavours, the > default policy in absence of a acpi=[off|force] kernel command line > parameter is to prefer DT over ACPI. > > This adds an option to invert that default policy, and prefer ACPI > over DT instead. Note that this policy is still superseded by the > value of the acpi= command line parameter. > Looks sane to me Reviewed-by: Graeme Gregory <graeme.gregory@linaro.org> G > Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> > --- > arch/arm64/Kconfig | 13 +++++++++++++ > arch/arm64/kernel/acpi.c | 3 ++- > 2 files changed, 15 insertions(+), 1 deletion(-) > > diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig > index 4f436220384f..f3aef40ad0ac 100644 > --- a/arch/arm64/Kconfig > +++ b/arch/arm64/Kconfig > @@ -918,6 +918,19 @@ config DMI > However, even with this option, the resultant kernel should > continue to boot on existing non-UEFI platforms. > > +config PREFER_ACPI_OVER_DT > + bool "Prefer booting via ACPI if both ACPI and DT are available" > + depends on ACPI > + help > + If both ACPI and DT platform descriptions are available, and the > + kernel was configured at build time to support both flavours, the > + default policy in absence of a acpi=[off|force] kernel command line > + parameter is to prefer DT over ACPI. > + > + This option inverts that default policy, by preferring ACPI over DT > + instead. Note that this default policy is still superseded by the > + value of the acpi= command line parameter. > + > endmenu > > menu "Userspace binary formats" > diff --git a/arch/arm64/kernel/acpi.c b/arch/arm64/kernel/acpi.c > index d1ce8e2f98b9..50ac056fb1fd 100644 > --- a/arch/arm64/kernel/acpi.c > +++ b/arch/arm64/kernel/acpi.c > @@ -188,7 +188,8 @@ void __init acpi_boot_table_init(void) > * and ACPI has not been force enabled (acpi=force) > */ > if (param_acpi_off || > - (!param_acpi_force && of_scan_flat_dt(dt_scan_depth1_nodes, NULL))) > + (!IS_ENABLED(CONFIG_PREFER_ACPI_OVER_DT) && > + !param_acpi_force && of_scan_flat_dt(dt_scan_depth1_nodes, NULL))) > return; > > /* > -- > 2.5.0 > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
On Mon, Apr 11, 2016 at 01:19:28PM +0200, Ard Biesheuvel wrote: > If both ACPI and DT platform descriptions are available, and the > kernel was configured at build time to support both flavours, the > default policy in absence of a acpi=[off|force] kernel command line > parameter is to prefer DT over ACPI. > > This adds an option to invert that default policy, and prefer ACPI > over DT instead. Note that this policy is still superseded by the > value of the acpi= command line parameter. Why do we need another method to specify an ACPI boot? I thought those vendors going for ACPI wouldn't be bothered with DT anyway. I'm not keen on having kernel builds with different behavior in respect of whether ACPI or DT is preferred. -- Catalin _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
On 12 April 2016 at 15:07, Catalin Marinas <catalin.marinas@arm.com> wrote: > On Mon, Apr 11, 2016 at 01:19:28PM +0200, Ard Biesheuvel wrote: >> If both ACPI and DT platform descriptions are available, and the >> kernel was configured at build time to support both flavours, the >> default policy in absence of a acpi=[off|force] kernel command line >> parameter is to prefer DT over ACPI. >> >> This adds an option to invert that default policy, and prefer ACPI >> over DT instead. Note that this policy is still superseded by the >> value of the acpi= command line parameter. > > Why do we need another method to specify an ACPI boot? I thought those > vendors going for ACPI wouldn't be bothered with DT anyway. > > I'm not keen on having kernel builds with different behavior in respect > of whether ACPI or DT is preferred. > How about adding support for acpi=on then? Currently, we only have acpi=off or acpi=force, and there is no way (i.e., for a distro installer) to boot via ACPI if it can but fall back to DT otherwise. Some enterprise features (like RAS) depend on ACPI boot so it may simply preferred but not mandated in some cases. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
On Tue, Apr 12, 2016 at 03:19:58PM +0200, Ard Biesheuvel wrote: > On 12 April 2016 at 15:07, Catalin Marinas <catalin.marinas@arm.com> wrote: > > On Mon, Apr 11, 2016 at 01:19:28PM +0200, Ard Biesheuvel wrote: > >> If both ACPI and DT platform descriptions are available, and the > >> kernel was configured at build time to support both flavours, the > >> default policy in absence of a acpi=[off|force] kernel command line > >> parameter is to prefer DT over ACPI. > >> > >> This adds an option to invert that default policy, and prefer ACPI > >> over DT instead. Note that this policy is still superseded by the > >> value of the acpi= command line parameter. > > > > Why do we need another method to specify an ACPI boot? I thought those > > vendors going for ACPI wouldn't be bothered with DT anyway. > > > > I'm not keen on having kernel builds with different behavior in respect > > of whether ACPI or DT is preferred. > > How about adding support for acpi=on then? Currently, we only have > acpi=off or acpi=force, and there is no way (i.e., for a distro > installer) to boot via ACPI if it can but fall back to DT otherwise. > Some enterprise features (like RAS) depend on ACPI boot so it may > simply preferred but not mandated in some cases. Since this is a distro preference, I would rather have an acpi=on option. -- Catalin _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
On Tue, Apr 12, 2016 at 12:41:23PM -0700, Roy Franz (HPE) wrote: > On Tue, Apr 12, 2016 at 6:35 AM, Catalin Marinas > <catalin.marinas@arm.com> wrote: > > On Tue, Apr 12, 2016 at 03:19:58PM +0200, Ard Biesheuvel wrote: > >> On 12 April 2016 at 15:07, Catalin Marinas <catalin.marinas@arm.com> wrote: > >> > On Mon, Apr 11, 2016 at 01:19:28PM +0200, Ard Biesheuvel wrote: > >> >> If both ACPI and DT platform descriptions are available, and the > >> >> kernel was configured at build time to support both flavours, the > >> >> default policy in absence of a acpi=[off|force] kernel command line > >> >> parameter is to prefer DT over ACPI. > >> >> > >> >> This adds an option to invert that default policy, and prefer ACPI > >> >> over DT instead. Note that this policy is still superseded by the > >> >> value of the acpi= command line parameter. > >> > > >> > Why do we need another method to specify an ACPI boot? I thought those > >> > vendors going for ACPI wouldn't be bothered with DT anyway. > >> > > >> > I'm not keen on having kernel builds with different behavior in respect > >> > of whether ACPI or DT is preferred. > >> > >> How about adding support for acpi=on then? Currently, we only have > >> acpi=off or acpi=force, and there is no way (i.e., for a distro > >> installer) to boot via ACPI if it can but fall back to DT otherwise. > >> Some enterprise features (like RAS) depend on ACPI boot so it may > >> simply preferred but not mandated in some cases. > > > > Since this is a distro preference, I would rather have an acpi=on > > option. > > While this is a 'distro preference', I think it is somewhat ugly for > this to be configured on the commandline. We (HPE) don't support DT, > and I don't think that is likely to change. While we control the > firmware for our main internal platform, and don't provide a DT there, > we also do development and testing on other platforms where the > firmware may provide a DT, but we never want to use it. This requires > developers/users to specify "acpi=force" on the command-line to boot > in a supported manner. You wrongly assume that everyone wants ACPI by generalising "we" (HPE) to "developers/users". In an ideal world where both ACPI and DT (if provided by firmware) are equally supported, such option wouldn't be much of an issue. But we are not there yet with some platforms having ACPI in an experimental state or relying on distro-only kernel patches. This means that a _mainline_ kernel configured with such ACPI default on option would require an explicit acpi=off on the command line to boot with DT. Since you don't always know which kernel you'd run, you pretty much end up with an acpi= option on the command line permanently. Maybe those vendors providing both ACPI and DT have a good reason like ACPI support not ready. > I would much rather be able to configure the kernel to prefer (or even > unconditionally require) ACPI to boot, as this will be the normal, > default, and only supported way to boot for our platform, and I expect > this to also be the case in much of the enterprise space. I really don't care about which platform recommends ACPI or DT. What I care about is not having to enable certain config option depending on which platform you target as this leads to config fragmentation (think of single Image). I much prefer a clear kernel policy on whether ACPI or DT is used if both are provided by firmware and we've already made that call - DT takes precedence. > Since I don't think it is possible to build an arm64 kernel with only > ACPI, and no DT support, I think a kconfig option to select the > preferred HW description to be used is the better solution. The (multi-platform, single Image) kernel is not in a position to assess whether ACPI or DT is in a better state for a given SoC. We should leave this "ACPI preferred" choice to the code running before the kernel by simply providing only ACPI tables. -- Catalin _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
On Wed, Apr 13, 2016 at 10:21:02AM -0700, Roy Franz wrote: > On 04/13/2016 06:59 AM, Catalin Marinas wrote: > >On Tue, Apr 12, 2016 at 12:41:23PM -0700, Roy Franz (HPE) wrote: > >>While this is a 'distro preference', I think it is somewhat ugly for > >>this to be configured on the commandline. We (HPE) don't support DT, > >>and I don't think that is likely to change. While we control the > >>firmware for our main internal platform, and don't provide a DT there, > >>we also do development and testing on other platforms where the > >>firmware may provide a DT, but we never want to use it. This requires > >>developers/users to specify "acpi=force" on the command-line to boot > >>in a supported manner. > > > >You wrongly assume that everyone wants ACPI by generalising "we" (HPE) > >to "developers/users". > > This is not what I am assuming or thinking. I think that a large enough set > of arm64 developers and users care primarily/only about ACPI, > and would benefit from not having to have an "acpi=xx" on the command-line > forevermore. That's to the detriment of those wanting to use DT on such platforms and would have to pass "acpi=off" (because I don't believe in different kernel images/configurations for different platforms). You may argue that no-one wants to use DT if the firmware also provides ACPI. As we currently stand, there are two main camps on ARM: 1. The DT one, unlikely to ever bother with ACPI for their platforms (e.g. mobile). This camp never cares about DT vs ACPI preference because their firmware would never provide the latter 2. The ACPI early adopters. Of these, there are two sub-categories: a) those who care about mainline Linux and provide a DT (in addition to ACPI) with their firmware as the more mature solution b) those who only run distro kernels with tons of patches and think that ACPI on ARM is ready, the last thing to solve being the boot priority As maintainer, I only care about (1) and (2.a). When ACPI on ARM will be mature enough and more feature-rich than DT (e.g. RAS features), we can revisit the ACPI vs DT boot priority, potentially making a switch without any additional config options. Who knows, maybe at that point no firmware will provide both DT and ACPI and we won't need to do anything in the kernel. But in the meantime, from a _mainline_ perspective, DT is considered the recommended/better supported option and the boot preference should only be overridden by users explicitly via command line arguments. -- Catalin _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 4f436220384f..f3aef40ad0ac 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -918,6 +918,19 @@ config DMI However, even with this option, the resultant kernel should continue to boot on existing non-UEFI platforms. +config PREFER_ACPI_OVER_DT + bool "Prefer booting via ACPI if both ACPI and DT are available" + depends on ACPI + help + If both ACPI and DT platform descriptions are available, and the + kernel was configured at build time to support both flavours, the + default policy in absence of a acpi=[off|force] kernel command line + parameter is to prefer DT over ACPI. + + This option inverts that default policy, by preferring ACPI over DT + instead. Note that this default policy is still superseded by the + value of the acpi= command line parameter. + endmenu menu "Userspace binary formats" diff --git a/arch/arm64/kernel/acpi.c b/arch/arm64/kernel/acpi.c index d1ce8e2f98b9..50ac056fb1fd 100644 --- a/arch/arm64/kernel/acpi.c +++ b/arch/arm64/kernel/acpi.c @@ -188,7 +188,8 @@ void __init acpi_boot_table_init(void) * and ACPI has not been force enabled (acpi=force) */ if (param_acpi_off || - (!param_acpi_force && of_scan_flat_dt(dt_scan_depth1_nodes, NULL))) + (!IS_ENABLED(CONFIG_PREFER_ACPI_OVER_DT) && + !param_acpi_force && of_scan_flat_dt(dt_scan_depth1_nodes, NULL))) return; /*
If both ACPI and DT platform descriptions are available, and the kernel was configured at build time to support both flavours, the default policy in absence of a acpi=[off|force] kernel command line parameter is to prefer DT over ACPI. This adds an option to invert that default policy, and prefer ACPI over DT instead. Note that this policy is still superseded by the value of the acpi= command line parameter. Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> --- arch/arm64/Kconfig | 13 +++++++++++++ arch/arm64/kernel/acpi.c | 3 ++- 2 files changed, 15 insertions(+), 1 deletion(-) -- 2.5.0 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel